1. Technical Field
The present disclosure relates to power management devices, and particularly to a mechanical power management device.
2. Description of Related Art
Many electronic devices, such as set-up boxes (STBs), use microcontrollers (MCUs) for power management. However, using MCUs to switch electronic devices on and off requires the installation of special control programs in the MCUs, which occupies system resources of the electronic devices. Therefore, mechanical switch devices are also widely used to switch the electronic devices on and off for conserving system resources of the electronic devices.
Mechanical switch devices generally include XOR gates. When an XOR gate is used in such a mechanical power management device, an output end of the XOR gate is connected to a control end of a power supply, one input end of the XOR gate is connected to a working voltage source through a switch, and the other input end of the XOR gate is connected to an output end of the power supply that is used to supply electric power to an electronic device.
When the electronic device is off, the switch is disconnected, and the two input ends and the output end of the XOR gate are all logic 0. To turn the electronic device on, the switch is operated to electrically connect the working voltage source to the input end of the XOR gate connected to the switch for a short time and then disconnect. Thus, the input end of the XOR gate connected to the switch is temporarily changed to be logic 1 by a working voltage. When the two input ends of the XOR gate are respectively logic 1 and logic 0, the output end of the XOR gate becomes logic 1. The logic 1 generated on the output end of the XOR gate controls the power supply to supply power to the electronic device, such that the electronic device is switched on, and the input end of the XOR gate connected to the output end of the power supply is also changed to logic 1. Because the switch only connects the working voltage source to the input end of the XOR gate for a short time and quickly disconnects, the input end of the XOR gate connected to the switch quickly returns to logic 0. Thus, the two input ends of the XOR gate are respectively logic 1 and logic 0, and the output end of the XOR gate stays at logic 1, such that the power supply is controlled to continuously supply power to the electronic device.
When the electronic device has already been switched on, and the switch is operated to electrically connect the working voltage source to the input end of the XOR gate connected to the switch for a short time and then quickly disconnect again, both the two input ends of the XOR gate become logic 1, and thus the output end of the XOR gate becomes logic 0. The logic 0 generated on the output end of the XOR gate prohibits the power supply supplying power to the electronic device, such that the electronic device is switched off and the input end of the XOR gate connected to the output end of the power supply returns to logic 0. When the switch disconnects and the input end of the XOR gate connected to the switch returns to logic 0, all of the two input ends and the output end of the XOR gate return to logic 0, and the electronic device remains off. In this way, operations applied to the switch can alternately switch the electronic device on and off, without using any software.
However, if the switch has already electrically connected the working voltage source to the input end of the XOR gate and does not quickly disconnect (e.g., due to being worn out, or errors in operations), the input end of the XOR gate connected to the switch will stay at logic 1 even when the input end of the XOR gate connected to the output end of the power supply has already become logic 1. In this situation, if the electronic device has been switched on by the electric connection between the working voltage source and the input end of the XOR gate, both the two input ends of the XOR gate being logic 1 makes the output end of the XOR gate to be logic 0, and the electronic device will be mistakenly switched off. If the electronic device has been switched off by the electric connection between the working voltage source and the input end of the XOR gate, the two input ends of the XOR gate being respectively logic 1 and logic 0 makes the output end of the XOR gate to be logic 1, and the electronic device will be mistakenly switched on.
Therefore, there is room for improvement within the art.